As yet, there is not a preventive measure that is known to be effective, even if applied at an early stage

Mike Rich, Action on Pre-eclampsia

Pre-eclampsia causes a pregnant woman's blood pressure to rise to very high levels.

This causes complications such as fluid retention and can lead to the condition eclampsia, which is associated with dangerous convulsions or liver or kidney failure, complications that can prove fatal.

The condition also increases the risk of premature delivery or emergency caesarean as delivery is the only real cure.

Pre-existing diabetes and high blood pressure have been identified as risk factors.

It is estimated by the campaign group Action on Pre-eclampsia that the condition affects one-in-10 pregnancies in the UK.

Our study raises the possibility of developing new approaches to diagnosis and intervention, which eventually could lead to preventive treatments

Dr Myles Wolf MGH Renal Unit

The researchers looked at blood samples from 4,500 taken from women in the first trimester of pregnancy.

Forty-five went on to develop pre-eclampsia.

Researchers compared their data to that of 90 women who had normal pregnancies

Women who went on to develop pre-eclampsia had reduced levels of the protein SHBG much more frequently than women who had normal pregnancies.

The risk associated with reduced levels did alter in line with weight, even though obese women are at higher risk of pre-eclampsia and tend to have insulin resistance, suggesting reduced first-trimester SHBG is the true risk factor.

Dr Myles Wolf, of the MGH Renal Unit, who led the research, said: "This study showed that a risk factor that can be detected many weeks before symptoms appear may be able to predict who will develop pre-eclampsia.

"Our study raises the possibility of developing new approaches to diagnosis and intervention, which eventually could lead to preventive treatments."

He added their work could provide a "window of opportunity" early in pregnancy when a preventative treatment might be successful.

Symptoms tend not to be seen until 20 to 25 weeks into a pregnancy.

Prevention

Dr Doris Campbell, reader in obstetrics and gynaecology at Aberdeen Maternity Hospital, told BBC News Online she was concerned that the study had identified a small number of women.

She added it was not the first time a protein had been identified as a potential marker for pre-eclampsia.

"There have been several others. Most of them have come to nothing."

But Mike Rich of Action on Pre-eclampsia said he believed it was the first time measurements of blood levels of SHBG in early pregnancy had been examined as a potential predictor for pre-eclampsia.

He said: "To have shown that a first trimester test could be predictive is novel.

"As yet, there is not a preventive measure that is known to be effective, even if applied at an early stage.

"However, if a test proved to be reliable then such measures could be developed more easily and targeted more precisely than they can be at the moment."

The report is published in the Journal of Clinical Endocrinology and Metabolism.